1. Field
The present disclosure is generally related to choosing a billing structure based on an amount of color in a document, and, in particular, to a system and method for determining a billing structure for outputting documents based on an estimation of color pixels in the document determined through processes utilizing image data when in device independent and device dependent states.
2. Description of Related Art
Image data comprises a number of pixels having a number of components that contribute to defining the image, such as color and intensity. The image data generally includes various color or gray levels, which contribute to the intensity of each pixel in the image. Each pixel of the image is assigned a number representing the amount of light or gray level for that space at that particular spot; i.e., the shade of gray in the pixel. Binary image data has two possible values for each pixel, black (represented by the number “1”) or white (represented by the number “0”). Images that have a large range of shades are referred to as grayscale images. For example, grayscale images have an 8-bit value per pixel comprising 256 tones or shades of gray for each pixel in the image (gray level of 0 to 255). Grayscale image data may also be referred to as continuous tone or contone image data. The pixels in a color image may be defined in terms of a color space, typically with three values, such as RGB—R for red, G for green, and B for blue—or four values, such as CMYK—C for cyan, M for magenta, Y for yellow, and K for black.
The pixels may also be defined in terms of device independent space (e.g., when inputting image data, such as standard RGB (sRGB) or CIE L*a*b) or a device dependent space (e.g., when outputting image data, such as RGB or CMYK). When outputting image data to an output device (e.g., copier, printer, or multi-function device (MFD)), a percentage scale may be used to identify how much ink is employed for a print job. Such information may typically be used for billing a customer for print jobs. For example, some methods employ a billing strategy based on an estimated amount of ink or toner consumption; others bill customers based on a print mode selection (e.g., draft, standard, color, enhanced, etc.) of the output device. In dynamic print job environments, because printing documents using black ink or toner is less expensive than using colored ink or toner, billing is often based on the amount of color content contained in the job to be printed. In order to bill customers for color printing, color detection is an important feature required in an image path. Color detection is used to analyze documents for presence of color as well as an amount of color in order to bill customers accordingly. Generally, the higher the presence and amount of color in a document, the higher the cost.
Some systems include counting the number of pixels in the image data of the document to be printed. For example, a number of binary pixels associated with the CMYK color planes may be counted to determine a pixel count for each category of color at the time of marking for output in the image path. Generally, with existing color detection and counting methods, a pixel will be labeled as color when the presence of any one of the C, M, and Y signals is detected. U.S. application Ser. No. 12/252,391 (published as Patent Application No. 2010/0100505 A1 on Apr. 22, 2010), filed Oct. 16, 2008 by the same Assignee (Xerox Corporation), which is hereby incorporated by reference in its entirety, proposes a way to count color pixels. In solid ink and ink jet products, however, it is desirable to render neutral gray objects with CMYK ink. This could substantially decrease the appearance of graininess in large uniform gray areas, such as a gray fill or sweep. For billing purposes, it is not desirable to charge customer for color pixels that were (are) supposed to be gray. The above-referenced '505 publication, for example, has limitations in handling images that are converted to contone from rendered binary data.
For copy path images, the C, M, and Y values of a pixel in a composite gray area could be quite different. In such images, many of these pixels can be labeled as color (although they may be rendered neutral gray), and thus counted as color pixels, which therefore skews the results used to determine the billing strategy. Such a classification may cause selection of a higher cost color billing strategy or a higher billing tier (selected from a multi-tier billing structure). Therefore, the customer may be billed for printing the document at a higher rate even though the output document reflects color pixels that are neutralized or gray.
Accordingly, an improved system and method of determining the amount of marked color content in a document and correctly billing customers is desirable.